The builders of Stonehenge are indeed mysterious. There has long been a misapprehension that the Celts built the monument, but it had in fact been there for about two thousand years before the Celts even arrived in Britain. They probably used Stonehenge, but whether they put it to the use its creators intended is unknowable. So who were these mysterious pre-Celtic Britons? Well, they were a late neolithic people (the neolithic period in Britain ran from about 5,500 B.C. to c. 2,500 B.C), who began to practise agriculture, albeit not terribly skillfully, in about 4,000 B.C. In addition to building Stonehenge, and a number of other "henges", they are also believed to have been responsible for a number of the gigantic carvings on chalk hills in the south of England, such as the White Horse of Uffington:

Beyond that, we really don't know much about them, or what became of them, so the discovery of the seasonal village near Stonehenge, apparently associated with rituals at the henge itself, could turn out to be very, very important. Encouragingly, the archaeologists have discovered a great number of small artifacts, which will aid greatly in establishing typologies for neolithic pottery, etc. In short, it's a big find, and one that archaeologists working in the field of neolithic studies should be very excited about.